CVE-2020-26242: Denial of Service in github.com/holiman/uint256

Background

The package github.com/holiman/uint256 is written in Go and provides functionality for working with 256-bit unsigned integers. It offers various mathematical operations such as addition, division, modulus, and multiplication. This package is vulnerable to a denial of service attack due to improper bounds checking in certain mathematical operations. If untrusted user inputs are processed using this package, an attacker can exploit this vulnerability to cause a panic and disrupt the application's normal functioning.

Vulnerability Detail

The vulnerability in github.com/holiman/uint256 arises from the lack of proper bounds checking in certain mathematical operations. This can lead to an out of bounds read, resulting in a panic. An attacker can leverage this vulnerability to launch a denial of service attack by providing malicious inputs that trigger the panic. The impact of this vulnerability can be severe, as it can cause the affected application to become unresponsive or crash, leading to service disruption. The vulnerability has been assigned the identifier CVE-2020-26242 and is also tracked as GHSA-jm5c-rv3w-w83m.

go get github.com/holiman/uint256@v1.1.1

Workaround

If updating the package is not immediately feasible, a possible workaround is to implement additional input validation and bounds checking in the application code that utilizes the github.com/holiman/uint256 package. By validating and sanitizing user inputs before passing them to the vulnerable operations, the risk of triggering the vulnerability can be mitigated. Here is an example of how input validation can be performed for the 'AddMod' operation:

def func AddModWrapper(a, b, modulus *uint256.Int) *uint256.Int {
    if a == nil || b == nil || modulus == nil {
        // Handle invalid inputs
        return nil
    }
    // Perform input validation and bounds checking
    if a.Cmp(modulus) >= 0 || b.Cmp(modulus) >= 0 {
        // Handle out of bounds inputs
        return nil
    }
    // Call the vulnerable operation
    return a.AddMod(b, modulus)
}

Conclusion

The vulnerability in github.com/holiman/uint256 can lead to a denial of service attack if untrusted user inputs are processed using this package. It is crucial to update the package to version 1.1.1 or later to mitigate the vulnerability. Alternatively, implementing additional input validation and bounds checking in the application code can provide a temporary workaround. For further assistance and support in addressing this vulnerability, please contact DevNack.com.

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